COST OF REVENUE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cost of Revenue [Abstract]
Compensation and benefits	$ 200,486	$ 240,487	$ 264,796
Outside fees and services	278,380	325,459	301,116
Cost of real estate sold	47,659	24,398	1,040
Reimbursable expenses	30,039	39,912	52,011
Technology and telecommunications	41,588	42,340	44,295
Depreciation and amortization	24,013	27,269	26,787
Total	$ 622,165	$ 699,865	$ 690,045